feat(psbt): easier custom transaction types

Issue: BG-47820

Author: reardencode

src/index.d.ts

@@ -8,7 +8,7 @@ import * as ScriptSignature from './script_signature';
 export { ScriptSignature, address, crypto, networks, payments, script, taproot, };
 export { Block } from './block';
 export { TaggedHashPrefix } from './crypto';
-export { Psbt, PsbtTxInput, PsbtTxOutput, Signer, SignerAsync, HDSigner, HDSignerAsync, } from './psbt';
+export { Psbt, PsbtTransaction, PsbtTxInput, PsbtTxOutput, Signer, SignerAsync, HDSigner, HDSignerAsync, } from './psbt';
 export { OPS as opcodes } from './ops';
 export { Transaction } from './transaction';
 export { Network } from './networks';

src/index.js

@@ -1,6 +1,6 @@
 'use strict';
 Object.defineProperty(exports, '__esModule', { value: true });
-exports.Transaction = exports.opcodes = exports.Psbt = exports.Block = exports.taproot = exports.script = exports.payments = exports.networks = exports.crypto = exports.address = exports.ScriptSignature = void 0;
+exports.Transaction = exports.opcodes = exports.PsbtTransaction = exports.Psbt = exports.Block = exports.taproot = exports.script = exports.payments = exports.networks = exports.crypto = exports.address = exports.ScriptSignature = void 0;
 const address = require('./address');
 exports.address = address;
 const crypto = require('./crypto');
@@ -29,6 +29,12 @@ Object.defineProperty(exports, 'Psbt', {
     return psbt_1.Psbt;
   },
 });
+Object.defineProperty(exports, 'PsbtTransaction', {
+  enumerable: true,
+  get: function() {
+    return psbt_1.PsbtTransaction;
+  },
+});
 var ops_1 = require('./ops');
 Object.defineProperty(exports, 'opcodes', {
   enumerable: true,

src/psbt.d.ts

@@ -1,6 +1,6 @@
 /// <reference types="node" />
 import { Psbt as PsbtBase } from 'bip174';
-import { KeyValue, PsbtGlobalUpdate, PsbtInput, PsbtInputUpdate, PsbtOutput, PsbtOutputUpdate } from 'bip174/src/lib/interfaces';
+import { KeyValue, PsbtGlobalUpdate, PsbtInput, PsbtInputUpdate, PsbtOutput, PsbtOutputUpdate, Transaction as ITransaction } from 'bip174/src/lib/interfaces';
 import { Network } from './networks';
 import { Transaction } from './transaction';
 export interface TransactionInput {
@@ -163,6 +163,24 @@ export interface SignerAsync {
     sign(hash: Buffer, lowR?: boolean): Promise<Buffer>;
     getPublicKey?(): Buffer;
 }
+/**
+ * This class implements the Transaction interface from bip174 library.
+ * It contains a bitcoinjs-lib Transaction object.
+ */
+export declare class PsbtTransaction implements ITransaction {
+    tx: Transaction<bigint>;
+    constructor({ tx, buffer, }?: {
+        tx?: Transaction<bigint>;
+        buffer?: Buffer;
+    });
+    getInputOutputCounts(): {
+        inputCount: number;
+        outputCount: number;
+    };
+    addInput(input: any): void;
+    addOutput(output: any): void;
+    toBuffer(): Buffer;
+}
 /**
  * This function must do two things:
  * 1. Check if the `input` can be finalized. If it can not be finalized, throw.

src/psbt.js

@@ -1,6 +1,6 @@
 'use strict';
 Object.defineProperty(exports, '__esModule', { value: true });
-exports.Psbt = void 0;
+exports.PsbtTransaction = exports.Psbt = void 0;
 const bip174_1 = require('bip174');
 const varuint = require('bip174/src/lib/converter/varint');
 const utils_1 = require('bip174/src/lib/utils');
@@ -613,14 +613,23 @@ exports.Psbt = Psbt;
  * It takes the "transaction buffer" portion of the psbt buffer and returns a
  * Transaction (From the bip174 library) interface.
  */
-const transactionFromBuffer = buffer => new PsbtTransaction(buffer);
+const transactionFromBuffer = buffer => new PsbtTransaction({ buffer });
 /**
  * This class implements the Transaction interface from bip174 library.
  * It contains a bitcoinjs-lib Transaction object.
  */
 class PsbtTransaction {
-  constructor(buffer = Buffer.from([2, 0, 0, 0, 0, 0, 0, 0, 0, 0])) {
-    this.tx = transaction_1.Transaction.fromBuffer(buffer, undefined, 'bigint');
+  constructor({ tx, buffer } = {}) {
+    if (tx !== undefined) {
+      this.tx = tx;
+    } else {
+      buffer = buffer || Buffer.from([2, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+      this.tx = transaction_1.Transaction.fromBuffer(
+        buffer,
+        undefined,
+        'bigint',
+      );
+    }
     checkTxEmpty(this.tx);
     Object.defineProperty(this, 'tx', {
       enumerable: false,
@@ -663,6 +672,7 @@ class PsbtTransaction {
     return this.tx.toBuffer();
   }
 }
+exports.PsbtTransaction = PsbtTransaction;
 function canFinalize(input, script, scriptType) {
   switch (scriptType) {
     case 'pubkey':

ts_src/index.ts

@@ -20,6 +20,7 @@ export { Block } from './block';
 export { TaggedHashPrefix } from './crypto';
 export {
   Psbt,
+  PsbtTransaction,
   PsbtTxInput,
   PsbtTxOutput,
   Signer,

ts_src/psbt.ts

@@ -831,16 +831,24 @@ export interface SignerAsync {
  */
 const transactionFromBuffer: TransactionFromBuffer = (
   buffer: Buffer,
-): ITransaction => new PsbtTransaction(buffer);
+): ITransaction => new PsbtTransaction({ buffer });
 
 /**
  * This class implements the Transaction interface from bip174 library.
  * It contains a bitcoinjs-lib Transaction object.
  */
-class PsbtTransaction implements ITransaction {
+export class PsbtTransaction implements ITransaction {
   tx: Transaction<bigint>;
-  constructor(buffer: Buffer = Buffer.from([2, 0, 0, 0, 0, 0, 0, 0, 0, 0])) {
-    this.tx = Transaction.fromBuffer<bigint>(buffer, undefined, 'bigint');
+  constructor({
+    tx,
+    buffer,
+  }: { tx?: Transaction<bigint>; buffer?: Buffer } = {}) {
+    if (tx !== undefined) {
+      this.tx = tx;
+    } else {
+      buffer = buffer || Buffer.from([2, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
+      this.tx = Transaction.fromBuffer<bigint>(buffer, undefined, 'bigint');
+    }
     checkTxEmpty(this.tx);
     Object.defineProperty(this, 'tx', {
       enumerable: false,